1. Field of the Invention
The present invention relates to a valve timing adjusting device in which the open-close timing of a suction valve and/or an exhaust valve of an internal-combustion engine (hereinafter, called an engine) is changed according to operation conditions of the engine.
2. Description of Related Art
Various valve timing adjusting devices have been proposed. In these devices, an open-close timing of a suction valve and/or an open-close timing of an exhaust valve in an engine are adjusted.
FIG. 7 is a horizontal sectional view of an internal structure of a vane type valve timing adjusting device having a plurality of conventional sealing units, and FIG. 8 is a vertical sectional view taken along line Axe2x80x94A of FIG. 7. In FIG. 7 and FIG. 8, referential numeral 1 indicates a housing. The housing 1 is connected with a crank shaft (not shown) denoting an output shaft of an engine through a chain (not shown). In the housing 1, a sprocket 2 rotated with the crank shaft, a casing 3 having a plurality of shoes 3a and a cover 4 formed in an annulus ring shape are integrally formed with each other by using a plurality of fixing members 5 such as bolts. The shoes 3a protrude from an internal circumferential surface of the casing 3 so as to form a plurality of hydraulic oil chambers. A front side portion of the casing 3 is covered with the cover 4. Also, a rotor 6 is arranged in the housing 1 to allow rotational motion relative to the casing 3. The rotor 6 is fixed to a camshaft 7 by a fixing member 8 such as a bolt. Therefore, the rotational motion of the camshaft 7 relative to the output shaft of the engine is allowed. The camshaft 7 relates to an open-close operation of a suction valve or an exhaust valve. The rotor 6 has a plurality of vanes 6a. Each vane 6a partitions the corresponding hydraulic oil chamber surrounded by the corresponding shoes 3a of the casing 3 into a hydraulic oil chamber 9 for timing advance and a hydraulic oil chamber 10 for timing retard. Also, a plurality of first oil passages 11 and a plurality of second oil passages 12 are arranged in the camshaft 7. Oil is supplied or discharged to/from each hydraulic oil chamber 9 for timing advance through the corresponding first oil passage 11, and oil is supplied or discharged to/from each hydraulic oil chamber 10 for timing retard through the corresponding second oil passage 12.
Also, to prevent oil leakage occurred between each hydraulic oil chamber 9 for timing advance and one hydraulic oil chamber 10 for timing retard adjacent to the hydraulic oil chamber 9 for timing advance, an axial directional slit 13 extending in an axial direction of the rotor 6 is formed in a top portion of the each shoe 3a of the casing 3, an axial directional slit 14 extending in an axial direction of the rotor 6 is formed in a top portion of the each vane 6a of the rotor 6, and a conventional sealing unit 101 is arranged in each axial directional slit 13 and axial directional slit 14.
Each conventional sealing unit 101 is composed of a sealing member 102 formed of resin and a metallic plate spring 103. Each sealing member 102 slides on an outer circumferential surface of the rotor 6 or an inner circumferential surface of the casing 3, each metallic plate spring 103 pushes the corresponding sealing member 102 toward the outer circumferential surface of the rotor 6 or the inner circumferential surface of the casing 3.
FIG. 9A is a diagonal view showing a structure of the conventional sealing unit 101 not yet arranged in the valve timing adjusting device, and FIG. 9B is a diagonal view showing a structure of the conventional sealing unit 101 which has been already arranged in the valve timing adjusting device. As shown in FIG. 9A and FIG. 9B, the sealing member 102 of each conventional sealing unit 101 has a seal reverse plane 102a parallel to a seal plane (not shown) and a pair of foot portions 102b protruding from both end portions of the seal reverse plane 102a, and the sealing member 102 is formed in a U-shaped section. The plate spring 103 of each conventional sealing unit 101 is composed of a central portion 103a formed in an arc shape and a pair of foot portions 103b placed on both ends of the central portion 103a. In this case, no connecting member is arranged to connect the sealing member 102 with the plate spring 103. Therefore, in cases where the conventional sealing unit 101 is not arranged in the valve timing adjusting device, as shown in FIG. 9A, the sealing member 102 and the plate spring 103 are separated from each other. When the conventional sealing unit 101 is arranged in the valve timing adjusting device, as shown in FIG. 9B, the foot portions 103b of the plate spring 103 are put on the seal reverse plane 102a of the sealing member 102, the valve timing adjusting device is laid down, and the sealing member 102 and the plate spring 103 are pushed into each axial directional slit 13 and axial directional slit 14 from the top while sliding on the surface of the slit. In this case, the height of the conventional sealing unit 101 is larger than a width of each axial directional slit 13 and axial directional slit 14 in a radial direction of the rotor 6. Therefore, the central portion 103a of the plate spring 103 is pressed hard by the wall of each axial directional slit 13 and axial directional slit 14, and the sealing member 102 and the plate spring 103 are substantially fixed to each other as a unit. Therefore, the sealing member 102 is pushed onto the outer circumferential surface of the rotor 6 or the inner circumferential surface of the casing 3 by the resilient force of the plate spring 103, and the oil leakage between each hydraulic oil chamber 10 for timing retard and the corresponding hydraulic oil chamber 9 for timing advance can be prevented.
However, because the conventional sealing unit 101 of the valve timing adjusting device has the above-described structure, it is required to lay the plate spring 103 having a small size on top of the sealing member 102 and to insert the sealing member 102 and the plate spring 103 into each axial directional slit 13 and axial directional slit 14 of the valve timing adjusting device while setting the sealing member 102 and the plate spring 103 in a standing state. Assuming that the sealing member 102 and the plate spring 103 are inserted into each slit of the valve timing adjusting device by hand, it is possible to arrange the sealing member 102 and the plate spring 103 in the valve timing adjusting device. In contrast, in cases where it is desired to arrange the sealing member 102 and the plate spring 103 in the valve timing adjusting device by using an automatic system, it is required to hold each axial directional slit 13 and axial directional slit 14 by using a chuck. In this case, because an opening of each axial directional slit 13 and axial directional slit 14 is narrow, it is difficult to obtain a chuck holding space from each axial directional slit 13 and axial directional slit 14. Therefore, it is difficult to reliably arrange the sealing member 102 and the plate spring 103 in the valve timing adjusting device. Also, in cases where the sealing member 102 and the plate spring 103 are fixed to each other by spot welding or screwing to make easy the arranging operation of the seal unit 101, an elastic coefficient of the plate spring 103 is increased when the plate spring 103 is inserted into the axial directional slit 13 or 14, and there is a problem that an excessive load is applied on the plate spring 103.
Also, the conventional sealing unit 101 is frequently used in the valve timing adjusting device. Therefore, in cases where it takes a lot of time to arrange the sealing units 101 in the axial directional slits 13 and 14 respectively, a manufacturing time required to manufacture the valve timing adjusting device is lengthened. Therefore, the arranging operation of the conventional sealing unit 101 is most important to perform the automatic manufacturing of the valve timing adjusting device.
Also, another sealing unit is disclosed in Published Unexamined Japanese Patent Application H11-30111 (1999). In this arranging method of the sealing unit, both end portions of a plate spring are respectively fitted to both ends of a sealing member formed in a U-shaped section, and the sealing unit is tightly inserted into a slit from the bottom side. In this sealing unit, the sealing member and the plate spring are connected with each other before the sealing unit is arranged in a valve timing adjusting device, and the arranging operation is easily performed. However, because the movement of the plate spring in a width direction of the sealing member is allowed, there is a high possibility that the plate spring is moved in the width direction of the sealing member and detaches from the sealing member.
Also, another sealing unit is disclosed in Published Unexamined Japanese Patent Application H10-331613 (1998). In this arranging method of the sealing unit, a plate spring formed in a wave shape is arranged in a sealing member formed in a C-shaped section, and the plate spring is exposed from a hole which is formed on a bottom surface of the sealing member. In this sealing unit, because the movement of the plate spring in any direction is prohibited, there is no possibility that the plate spring detaches from the sealing member. However, the plate spring is substantially fixed to the sealing member. Therefore, the elastic coefficient of the plate spring is increased in the same manner as in the above description, and there is a problem that an excessive load is applied on the plate spring.
An object of the present invention is to provide, with due consideration to the drawbacks of the valve timing adjusting device, a valve timing adjusting device in which a plate spring is reliably prevented from detaching from a sealing member without giving a large load to the plate spring.
The object is achieved by the provision of a valve timing adjusting device comprising an output shaft of an internal-combustion engine, a casing which is fixed to the output shaft and has a plurality of shoes protruding from an internal circumferential surface to form a plurality of hydraulic oil chambers, a rotor which is arranged in the casing so as to be fixed to a camshaft and has a plurality of vanes to partition each hydraulic oil chamber of the casing into a hydraulic oil chamber for timing advance and a hydraulic oil chamber for timing retard, and a sealing unit, which is arranged between the rotor and the casing, for preventing oil leakage between one hydraulic oil chamber for timing advance and one hydraulic oil chamber for timing retard adjacent to the hydraulic oil chamber for timing advance. Rotational motion of the rotor relative to the casing is allowed to change a rotational phase of the camshaft relative to the output shaft. The sealing unit comprises a sealing member having both a seal plane sliding on an inner wall surface of the hydraulic oil chamber for timing advance or the hydraulic oil chamber for timing retard and a seal reverse plane parallel to the seal plane, a plate spring for pushing the seal reverse plane of the sealing member toward the inner wall surface of the hydraulic oil chamber for timing advance or the hydraulic oil chamber for timing retard, and plate spring detachment preventing means. The plate spring detachment preventing means comprises a protruding member, which protrudes from the seal reverse plane of the sealing member, for restricting the movement of the plate spring along the seal reverse plane of the sealing member within a prescribed range, and a detachment stopping member, which is arranged on the top of the protruding member, for restricting the movement of the plate spring away from the seal reverse plane of the sealing member within another prescribed range.
In the above configuration, the movement of the plate spring along the seal reverse plane of the sealing member is restricted within a prescribed range by the protruding member. Also, the movement of the plate spring away from the seal reverse plane of the sealing member is restricted within another prescribed range by the detachment stopping member. Therefore, the plate spring does not detach from the seal member after the fitting of the plate spring to the seal member. Also, when the seal unit is arranged in the valve timing adjusting device while bending the plate spring, the plate spring does not collide with the seal member.
Accordingly, no excessive load is applied on the plate spring, and the plate spring can be reliably prevented from detaching from the seal member when the seal unit is arranged in the valve timing adjusting device.
It is preferred that the detachment stopping member of the plate spring detachment preventing means is obtained by deforming a top portion of the protruding member according to ultrasonic wave machining method.
Accordingly, time required to fit the plate spring to the seal member can be shortened as compared with another fitting method. Also, a degree of a length change of the plate spring is stable. Therefore, the manufacturing time of the valve timing adjusting device assembled by using an automatic assembly line can be shortened, and the quality of the valve timing adjusting device can be stabilized.
It is preferred that the sealing member has a pair of foot portions protruding from both ends of the seal reverse plane respectively and is formed in a U-shaped section, and the protruding member of the plate spring detachment preventing means is formed of a pair of protruding portions which respectively protrude from the seal reverse plane along the foot portions.
Accordingly, the movement of the plate spring along the seal reverse plane of the sealing member is restricted within a prescribed range by the pair of protruding portions.
It is preferred that the sealing member is formed in a box shape and has a wall protruding from an end of the seal reverse plane, and the protruding member of the plate spring detachment preventing means protrudes from the seal reverse plane along an inner surface of the wall of the sealing member.
Accordingly, the movement of the plate spring along the seal reverse plane of the sealing member is restricted within a prescribed range by the protruding member.
It is preferred that the plate spring has a cut-out opening to position the plate spring by using a chuck of an automatic system to fit the plate spring to the sealing member.
Accordingly, the plate spring can be held by the chuck on the automatic assembly line until the plate spring is brought down on the seal reverse surface.